Experimental study of histopathological lesions induced by ornithobacterium rhinotracheale infection followed inoculation with H9N2 avian influenza virus

Avian influenza virus as a primary agent causes histopathologic lesions in infected chickens. Although, it was not any complete histopathologic study of ORT effects on chickens infected with avian influenza virus. The purpose of this study was to evaluate histopathological lesions induced by secondary infection with Ornithobacterium rhinotracheale on infected specific pathogen-free (SPF) chickens with H9N2 AI virus. Sixty, one-day-old SPF chicks were provided and divided randomly into three groups. At 21 days, the chicks in the group 1 were inoculated with H9N2 AI virus, group 2 was first infected by AI virus and 3 days later inoculated by ORT. Each bird in control group was inoculated with PBS. Then, the birds were euthanized and examined for histopathological lesions. The samples from various tissues were collected at 2, 4, 6, 8, 10, 12, 14 and 16 days post-inoculation (DPI). Histologic lesions in infected groups were observed as follow: congestion and hyperplasia of epithelium in trachea, pneumonia, hemorrhage and urinary tubules necrosis in kidneys, congestion of sinusoid spaces and portal vein in liver, lymphocyte depletion in the bursa of fabricius, hyperplasia of lymphoid Follicles in spleen, congestion and heterophil infiltration in thymus and increased of lymphoid Follicles in cecal tonsil. The results of this study showed that infected chickens by H9N2 AI virus under secondary infection with ORT cause increased histopathological lesions induced by virus.